The present invention relates to a surgical laser beam-based alignment system and method including the use of a narrow, straight beam of light from a low voltage laser device to determine correct alignment in total knee, hip and back surgery. In orthopedic surgery it is essential that correct alignment be obtained for successful results. It is well known that failure to correctly align a total knee arthroplasty, for example, leads to premature failure of the prosthesis. In the past, extramedullary rods, intramedullary rods and flexible cords have been used to assist the surgeon in this important task. These methods all have their potential problems and can lead to failure or injure the patient. In the case of the extramedullary alignment method, the center of the femoral head has to be radiologically determined and marked externally on the patient. The use of trial and error to find the center of the femoral head and accurately locate the external marker on the patient is time-consuming. Also, improper positioning of the x-ray machine with respect to the center of the femoral head and the distance from the x-ray machine to the radiographic cassette introduces the error factor known as "parallax". Also, alignment rods presently used have to be extended away from the center of the rotation of the bone and, consequently, there can be a significant error with any rotation of the distal femur from neutral. For these reasons, extramedullary alignment of the distal femur fell out of favor in the late 1980s and the intramedullary rod alignment system became popular. With the intramedullary rod, the rod is placed through a drill hole in the intracondylar notch into the femoral canal and a predetermined difference between the anatomical axis of the femur and the mechanical axis, the so-called tibial femoral angle, is dialed in by mechanical means and the perpendicular cut is then made through the transverse axis. Unfortunately, there are a number of inherent errors in intramedullary alignment means. Not uncommonly, the intramedullary canal is quite large in diameter and the rod can be misaligned up against one cortex or the other. An error caused by a large intramedullary canal can be up to 2-3 degrees. Because the intramedullary rod is hidden from the surgeon's view, he has no way of determining this inherent error. Also, the intramedullary canal in the sagittal plane is curvalinear, and can cause mispositioning of the rod depending upon the location of the entrance hole, either in the anterior or posterior direction, causing the rod to be an inaccurate means of determining a perpendicular cut on the femur in the sagittal plane. It is becoming apparent that intramedullary rods can be dangerous and even lethal when used to align a total knee resection. Recent studies have shown a tremendous release of fat emboli into the circulation upon release of the tourniquet after total knee arthroplasty. A number of deaths have been reported secondary to this complication. Ideally, a reliable, non-invasive extramedullary system would be much safer for the patient.
It is with these issues in mind that the present invention was developed.